For insurance you've got to find an insurance company that is cool with the idea of a converted RV. You'll be insured as an RV in the end, but some companies are confused about the fact that you made your RV. From reading some forums on Skoolie.net, State Farm (the insurance my family uses) is pretty cool about insuring buses. As far as transporting a bus when you first buy it, the internet suggests insuring it right when you get it, if not for realsies than at least with a temporary (30 day) trip insurance so you can drive it to its new home. This sounds tempting to me since I don't think I'll be driving it much when I first get it, though that could change. I am anticipating driving it to Berkeley, finding a parking space and only moving it around the block every few weeks to not get tickets. I plan to park it in the neighborhood near my work (there are lots of other rvs/buses parked in the area) and then I can use the shop at my work to work on it after hours!
As far as registration goes there is some solid info and some grey areas. The solid info is what you do when you register it as an rv. It differs by state but the gist seems to be that you've got to prove its an rv by having some combo of a bed, electricity, stove, refrigerator, heating and toilet. Some states seem to want you to have receipts for these things or do an inspection to prove you've got it. Luckily it is sounding like Oregon just needs you to sign a paper saying you've got it. No proof needed. So theoretically I could re register it before I finish converting it. It may be easier though to wait until its partially finished (maybe by when I bring it back to Oregon in July) to re register. The reason you should re register as an rv is that most buses require a commercial drivers license. The internet's advice on when you buy a bus is to drive it home sans correct registration (and hope for the best. Everyone had stories of having no problems) and to wait until you've done the bulk of the conversion before re registering. Another thing I am kind of hoping for though is that this bus I'm currently looking at may be registered as a van or automobile since its small. Then I'd have to look at my options and see if its worth it to re register. It may come down to insurance at that point and also prices of registration. We shall see, more info is needed.
hooray spending money!